Infrared and Raman spectroscopic studies have been used to characterize conformational changes in the gel and liquid crystalline forms of simple model membrane systems. Schemes were devised for determining reliable, integrated intensities of the C-H stretching mode region of lipid bilayers using a Raman spectrograph coupled to a multichannel diode array detector. This intensity probe is particularly sensitive to bilayer expansion effects, as, for example, the structural changes involved in the membrane pretransition.